        /**
         * Created by IntelliJ IDEA.
         * User: Taras_Brzezinsky
         * Date: 8/7/11
         * Time: 2:02 PM
         * To change this template use File | Settings | File Templates.
         */

        import java.io.BufferedReader;
        import java.io.InputStreamReader;
        import java.io.PrintWriter;
        import java.io.FileReader;
        import java.util.StringTokenizer;
        import java.io.IOException;
        import java.util.Arrays;

        public class Pants extends Thread {

            public Pants() {
                this.input = new BufferedReader(new InputStreamReader(System.in));
                this.output = new PrintWriter(System.out);
                this.setPriority(Thread.MAX_PRIORITY);
            }

            public void run() {
                try {
                    int n = nextInt();
                    long []A = new long [n];
                    for (int i = 0; i < n; ++i) {
                        A[i] = nextLong();
                    }
                    long answer = 0;
                    for (int i = 0; i < n; ++i) {
                        answer += A[i];
                        answer += (A[i] - 1) * i;
                    }
                    output.println(answer);
                    output.flush();
                    output.close();

                } catch (Throwable e) {
                    System.err.println(e.getMessage());
                    System.err.println(Arrays.deepToString(e.getStackTrace()));
                }
            }


            public static void main(String[] args) {
                new Pants().start();
            }

            private String nextToken() throws IOException {
                while (tokens == null || !tokens.hasMoreTokens()) {
                    tokens = new StringTokenizer(input.readLine());
                }
                return tokens.nextToken();
            }

            private int nextInt() throws IOException {
                return Integer.parseInt(nextToken());
            }

            private double nextDouble() throws IOException {
                return Double.parseDouble(nextToken());
            }

            private long nextLong() throws IOException {
                return Long.parseLong(nextToken());
            }


            private BufferedReader input;
            private PrintWriter output;
            private StringTokenizer tokens = null;
        }
